U.S. patent application number 12/277087 was filed with the patent office on 2010-05-27 for method and system for content distribution network performance and quality measurement.
This patent application is currently assigned to AT&T CORP.. Invention is credited to Sanjay MacWan.
Application Number | 20100128918 12/277087 |
Document ID | / |
Family ID | 42196297 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100128918 |
Kind Code |
A1 |
MacWan; Sanjay |
May 27, 2010 |
Method and System for Content Distribution Network Performance and
Quality Measurement
Abstract
A content delivery system includes an upload module, a content
delivery module, and a quality assurance module. The upload module
is configured to receive content from a content provider, and
generate an upload signature for the content as received from the
content provider. The content delivery module is configured to
receive a request for the content from a client system, and provide
the content to the client system. The quality assurance module is
configured to generate a download signature for the content as
delivered to the client, and compare the upload signature and the
download signature. When the upload signature and the download
signature do not match, the quality assurance module is further
configured to generate an alert.
Inventors: |
MacWan; Sanjay; (Marlboro,
NJ) |
Correspondence
Address: |
AT&T Legal Department - LNA;Attn: Patent Docketing
Room 2A- 207, One AT & T Way
Bedminster
NJ
07921
US
|
Assignee: |
AT&T CORP.
New York
NY
|
Family ID: |
42196297 |
Appl. No.: |
12/277087 |
Filed: |
November 24, 2008 |
Current U.S.
Class: |
382/100 |
Current CPC
Class: |
H04N 21/2402 20130101;
H04N 21/63 20130101; H04N 21/84 20130101; H04N 21/2358 20130101;
H04N 21/2408 20130101; H04N 21/814 20130101; H04N 21/23418
20130101 |
Class at
Publication: |
382/100 |
International
Class: |
G06K 9/00 20060101
G06K009/00 |
Claims
1. A content delivery system comprising: an upload module
configured to: receive content from a content provider; and
generate an upload signature for the content as received from the
content provider, the upload signature including a hash of the
content; and a content delivery module configured to: receive a
request for the content from a client system; and provide the
content to the client system; and a quality assurance module
configured to: generate a download signature for the content as
delivered to the client; compare the upload signature and the
download signature; and generate an alert when the upload signature
and the download signature do not match.
2. The content delivery system of claim 1 wherein the client system
is an autodownloader configured to periodically request content
from the content delivery system.
3. The content delivery system of claim 1 wherein the quality
assurance module can capture an image of the content as
delivered.
4. The content delivery system of claim 3 wherein the image is
provided to the content provider.
5. The content delivery system of claim 1 wherein the upload
signature further includes an upload signature for an embedded
content object of the content.
6. The content delivery system of claim 1 wherein the upload
signature further includes a combined upload signature of a
plurality of embedded content object of the content.
7. The content delivery system of claim 1 wherein the upload
signature further includes, a size of the content, a length of play
of the content, a format of the content, a location within a web
page of the content, a digital watermark embedded in the content,
or any combination thereof.
8. A computer-readable medium comprising a plurality of
instructions to manipulate a processor, the plurality of
instructions comprising: instructions to generate a download
signature for content as delivered to a client, the download
signature including a hash of the content; instructions to compare
an upload signature and the download signature, the upload
signature representing the content as received from a content
provider; and instructions to generate an alert when the upload
signature and the download signature do not match.
9. The computer-readable medium of claim 8 further comprising
instructions to capture an image of the content as delivered.
10. The computer-readable medium of claim 9 wherein the image is
provided to the content provider.
11. The computer-readable medium of claim 8 wherein the download
signature further includes a download signature for an embedded
content object of the content.
12. The computer-readable medium of claim 8 wherein the download
signature further includes a combined download signature of a
plurality of embedded content object of the content.
13. The computer-readable medium of claim 8 wherein the download
signature further includes a size of the content, a length of play
of the content, a format of the content, a location within a web
page of the content, a digital watermark embedded in the content,
or any combination thereof.
14. A edge server comprising: a processor configured to: receive a
request for the content from a client system; provide the content
to the client system; generate a download signature for the content
as delivered to the client, the download signature including a hash
of the content; compare an upload signature and the download
signature, the upload signature representing the content as
received from a content provider; and generate an alert when the
upload signature and the download signature do not match.
15. The edge server of claim 14 wherein the download signature
further includes a download signature for an embedded content
object of the content.
16. The edge server of claim 14 wherein the download signature
further includes a combined download signature of a plurality of
embedded content object of the content.
17. The edge server of claim 14 wherein the download signature
further includes a size of the content, a length of play of the
content, a format of the content, a location within a web page of
the content, a digital watermark embedded in the content, or any
combination thereof.
18. A quality assurance device comprising: a processor configured
to: receive content from a content distribution network: generate a
download signature for the content, the download signature
including a hash of the content; compare an upload signature and
the download signature, the upload signature representing the
content as received by the content distribution network from a
content provider; and generate an alert when the upload signature
and the download signature do not match.
19. The quality assurance device of claim 18, wherein the download
signature further includes a download signature for an embedded
content object of the content.
20. The quality assurance device of claim 18, wherein the download
signature further includes a combined download signature of a
plurality of embedded content object of the content.
21. The quality assurance device of claim 18, wherein the download
signature further includes a size of the content, a length of play
of the content, a format of the content, a location within a web
page of the content, a digital watermark embedded in the content,
or any combination thereof.
22. A computer-readable medium comprising a plurality of
instructions to manipulate a processor, the plurality of
instructions comprising: instructions to receive content from an
edge server of a content distribution network; instructions to
generate a download signature for the content, the download
signature including a hash of the content; and instructions to
provide the download signature to a quality assurance device of the
content distribution network.
23. The computer-readable medium of claim 22, wherein the download
signature further includes a download signature for an embedded
content object of the content.
24. The computer-readable medium of claim 22, wherein the download
signature further includes a combined download signature of a
plurality of embedded content object of the content.
25. The computer-readable medium of claim 22, wherein the download
signature further a size of the content, a length of play of the
content, a format of the content, a location within a web page of
the content, a digital watermark embedded in the content, or any
combination thereof.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure generally relates to communications
networks, and more particularly relates to a method and system for
Content Distribution Network (CDN) performance and quality
measurement.
BACKGROUND
[0002] Packet-switched networks, such as networks based on the
TCP/IP protocol suite, can distribute a rich array of digital
content to a variety of client applications. One popular
application is a personal computer browser for retrieving documents
over the Internet written in the Hypertext Markup Language (HTML).
Frequently, these documents include embedded content. Where once
the digital content consisted primarily of text and static images,
digital content has grown to include audio and video content as
well as dynamic content customized for an individual user.
[0003] It is often advantageous when distributing digital content
across a packet-switched network to divide the duty of answering
content requests among a plurality of geographically dispersed
servers. For example, popular Web sites on the Internet often
provide links to "mirror" sites that replicate original content at
a number of geographically dispersed locations. A more recent
alternative to mirroring is content distribution networks (CDNs)
that dynamically redirect content requests to an edge server
situated closer to the client issuing the request. CDNs either
co-locate edge servers within Internet Service Providers or deploy
them within their own separate networks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] It will be appreciated that for simplicity and clarity of
illustration, elements illustrated in the Figures have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements are exaggerated relative to other elements.
Embodiments incorporating teachings of the present disclosure are
shown and described with respect to the drawings presented herein,
in which:
[0005] FIG. 1 is a diagram illustrating a communications network in
accordance with one embodiment of the present disclosure;
[0006] FIG. 2 is block diagram illustrating an anycast CDN system
in accordance with one embodiment of the present disclosure;
[0007] FIG. 3 is block diagram illustrating another CDN system in
accordance with one embodiment of the present disclosure;
[0008] FIG. 4 is a flow diagram illustrating a method of measuring
performance and quality of a CDN; and
[0009] FIG. 5 is an illustrative embodiment of a general computer
system.
[0010] The use of the same reference symbols in different drawings
indicates similar or identical items.
DETAILED DESCRIPTION OF THE DRAWINGS
[0011] The numerous innovative teachings of the present application
will be described with particular reference to the presently
preferred exemplary embodiments. However, it should be understood
that this class of embodiments provides only a few examples of the
many advantageous uses of the innovative teachings herein. In
general, statements made in the specification of the present
application do not necessarily limit any of the various claimed
inventions. Moreover, some statements may apply to some inventive
features but not to others.
[0012] FIG. 1 shows a geographically dispersed network 100, such as
the Internet. Network 100 can include routers 102, 104, and 106
that communicate with each other and form an autonomous system (AS)
108. AS 108 can connect to other ASs that form network 100 through
peering points at routers 102 and 104. Additionally, AS 108 can
include client systems 110, 112, 114, and 116 connected to
respective routers 102, 104, and 106 to access the network 100.
Router 102 can provide ingress and egress for client system 110.
Similarly, router 104 can provide ingress and egress for client
system 112. Router 106 can provide ingress and egress for both of
client systems 114 and 116.
[0013] AS 108 can further include a Domain Name System (DNS) server
118. DNS server 118 can translate a human readable hostname, such
as www.att.com, into an Internet Protocol (IP) address. For
example, client system 110 can send a request to resolve a hostname
to DNS server 118. DNS server 118 can provide client system 110
with an IP address corresponding to the hostname. DNS server 118
may provide the IP address from a cache of hostname-IP address
pairs or may request the IP address corresponding to the hostname
from an authoritative DNS server for the domain to which the
hostname belongs.
[0014] Client systems 110, 112, 114, and 116 can retrieve
information from a server 120. For example, client system 112 can
retrieve a web page provided by server 120. Additionally, client
system 112 may download content files, such as graphic, audio, and
video content, and program files such as software updates, from
server 120. The time required for client system 112 to retrieve the
information from the server 120 normally is related to the size of
the file, the distance the information travels, and congestion
along the route. Additionally, the load on the server 120 is
related to the number of client systems 110, 112, 114, and 116 that
are actively retrieving information from the server 120. As such,
the resources such as processor, memory, and bandwidth available to
the server 120 limit the number of client systems 110, 112, 114,
and 116 that can simultaneously retrieve information from the
server 120.
[0015] Additionally, the network can include edge servers 122 and
124 replicating content on the server 120 that can be located more
closely within the network to the client systems 110, 112, 114, and
116. Edge server 122 can link to router 102, and edge server 124
can link to router 106. Client systems 110, 112, 114, and 116 can
be assigned edge server 122 or 124 to decrease the time needed to
retrieve information, such as by selecting the edge server closer
to the particular client system. The network distance between an
edge server and client system can be determined by network cost and
access time. As such, the effective network distance between the
edge server and the client system may be different from the
geographic distance.
[0016] When assigning edge servers 122 and 124 to client systems
110 through 116, the edge server closest to the client can be
selected. The closest edge server may be the edge server having a
shortest network distance, a lowest network cost, a lowest network
latency, a highest link capacity, or any combination thereof Client
system 110 can be assigned edge server 122, and client systems 114
and 116 can be assigned to edge server 124. The network costs of
assigning client system 112 to either of edge server 122 or 124 may
be substantially identical. When the network costs associated with
the link between router 102 and router 104 are marginally lower
than the network costs associated with the link between router 104
and router 106, client 112 may be assigned to edge server 124.
[0017] Client system 112 may send a request for information to edge
server 124. If edge server 124 has the information stored in a
cache, it can provide the information to client system 112. This
can decrease the distance the information travels and reduce the
time to retrieve the information. Alternatively, when edge server
124 does not have the information, it can retrieve the information
from server 120 prior to providing the information to the client
system 112. In an embodiment, edge server 124 may attempt to
retrieve the information from edge server 122 prior to retrieving
the information from server 120. The edge server 124 may retrieve
the information from the server 120 only once, reducing the load on
server 120 and network 100 such as, for example, when client system
114 requests the same information.
[0018] Edge server 124 can have a cache of a limited size. The
addition of new content to the cache may require old content to be
removed from the cache. The cache may utilize a least recently used
(LRU) policy, a least frequently used (LFU) policy, or another
cache policy known in the art. When the addition of relatively cold
or less popular content to the cache causes relatively hot or more
popular content to be removed from the cache, an additional request
for the relatively hot content can increase the time required to
provide the relatively hot content to the client system, such as
client system 114. To maximize the cost savings and time savings of
providing content from the cache, the most popular content may be
stored in the cache, while less popular content is retrieved from
server 120.
[0019] In an embodiment, network problems may prevent the
propagation of content through the CDN, resulting in a user
receiving incomplete or stale content. For example, an edge server
may not be able to retrieve content from another edge server or
from an origin server. In another example, the edge server
providing the content to the user may not be aware that a new
version of the content is available, resulting in stale content
being provided to the user. It is desirable to identify and correct
problems impacting the user experience relatively quickly in order
to minimize the number of users affected.
[0020] FIG. 2 illustrates an anycast CDN system 200 that can be
used in conjunction with communications network 100. The anycast
CDN system 200 can include a CDN provider network 202. The CDN
provider network 202 can include a plurality of provider edge
routers 204 through 214. The provider edge routers 204 through 214
can serve as ingress points for traffic destined for the CDN
provider network 202, and egress points for traffic from the CDN
provider network 202 destined for the rest of the Internet. The
anycast CDN system 200 can further include edge servers 216 and
218. Edge server 216 can receive traffic from the CDN provider
network 202 through provider edge router 204, and edge server 218
can receive traffic from the CDN provider network 202 through edge
cache router 214. In addition to providing CDN service to clients
within the CDN provider network, the anycast CDN system 200 can
provide CDN service to clients within AS 220 and AS 222. AS 220 can
include provider edge routers 224 and 226 with peering connections
to provider edge routers 206 and 208, respectively. Similarly, AS
222 can include provider edge routers 228 and 230 with peering
connections to provider edge routers 210 and 212 respectively.
Requests for content from systems within either AS 220 or AS 222
may enter the CDN provider network through the appropriate peering
points and be directed to either edge server 216 or 218.
[0021] Anycast CDN system 200 can also include a route controller
232. The route controller 232 can exchange routes with provider
edge routers 206 through 212 within the CDN provider network 202.
As such, the route controller 232 can influence the routes selected
by the provider edge routers 206 through 212. Additionally, the
route controller 232 can receive load information from edge servers
216 and 218.
[0022] Edge servers 216 and 218 can advertise, such as through
Border Gateway Protocol (BGP), a shared anycast address to the CDN
provider network 202, specifically to provider edge routers 204 and
214. Provider edge routers 204 and 214 can advertise the anycast
address to the route controller 232. The route controller 232 can
provide a route to the anycast address to each of the provider edge
routers 206 though 212. Provider edge routers 206 through 212 can
direct traffic addressed to the anycast address to either of the
edge servers 216 and 218 based on the routes provided by the route
controller 232. Additionally, the provider edge routers 206 through
212 can advertise the anycast address to AS 220 and AS 222. The
route controller 232 can manipulate the route provided to provider
edge routers 206 through 212 based on the load on the edge servers
216 and 218, network bandwidth, network cost, network distance, or
any combination thereof. Altering the route to the anycast address
can change which of edge servers 216 and 218 serve content to
client systems within the CDN provider network 202, AS 220, and AS
222.
[0023] In an embodiment, AS 220 may be an unstable network. Traffic
from client systems within the AS 220 may enter the CDN provider
network 202 at both provider edge routers 206 and 208. When anycast
traffic from the same client system enters the CDN provider network
202 at both provider edge routers 206 and 208, portions of the
traffic may be directed to different edge servers 216 and 218.
Persistent and/or secure connections may be disrupted when portions
of the traffic are sent to different edge servers 216 and 218. As
such, it is undesirable to provide an anycast addresses to client
systems within an unstable network.
[0024] FIG. 3 illustrates another embodiment of a CDN system 300
that can be in conjunction with communications network 100 and/or
anycast CDN system 200. A content provider 302 can upload content
to the CDN system 300 through an upload module 304. The upload
module 304 can distribute the content to the content delivery
module 306 which can distribute the content to client systems 308
requesting the content. The content may be distributed to the
content delivery module 306 prior to a request from client systems
308 and in response to a request from client systems 308.
[0025] In an embodiment, the upload module 304 can generate an
upload signature representing the content as received by the upload
module 304. Similarly, the content delivery module 306 can generate
a download signature representing the content as provided to the
client systems 308. The upload signature and the download signature
can be provided to a quality assurance module 310. In an
embodiment, client systems 308 may generate a download signature of
the content as received and provide the download signature to the
quality assurance module 3 10. The quality assurance module 310 can
compare the upload and download signatures for the content and
determine if the content experience provided to the client systems
308 matches the experience intended by the content provider. If the
upload and download signatures do not match, the quality assurance
module can generate an alert including notifying CDN support staff
of the issue. Preferably, the CDN support staff can promptly
resolve the issue.
[0026] The upload module 304, the content delivery module 306, and
the quality assurance module 310 can be implemented in hardware,
software, or any combination thereof. Each module may include one
or more computer systems. When a module includes more than one
computer system, the functions of the module can be distributed
across the multiple computer systems in a symmetric manner, i.e.,
each computer system performs the same type of tasks, or in an
asymmetric manner, i.e., two computer systems of the module may
perform different tasks.
[0027] FIG. 4 illustrates a method of monitoring the quality of a
CDN, such as CDN 200. At 402, the CDN receives content from a
content provider. For example, the content can be a web page with
several embedded content objects, such a multimedia content, image
content, textual content, and the like. At 404, an upload signature
can be generated for the content. The upload signature can be a
representation of the content as received from the content provider
by the CDN. The signature can be derived from a variety of
attributes including a size of the content, a length of play of
audio or video content, a format of the content, a hash of the
content, a location within a web page where the content appears, a
digital watermark embedded in the content, other content
properties, and the like. In an embodiment, the upload signature
can include a separate signature for each embedded content object.
In another embodiment, the upload signature can include a combined
signature for the content including any embedded objects. In yet
another embodiment, the content signature can be a signature
generated through the combination of the signatures for each
embedded object.
[0028] At 406, the CDN can receive a request for the content from a
client system, such as client system 110. At 408, an edge server of
the CDN, such as edge server 122, can provide the content to the
client system. At 410, a download signature can be generated for
the content. The download signature can be a representation of the
content as provided by the CDN to the client system. In an
embodiment, the download signature can be determined by the edge
server providing the content or by the client system. In an
embodiment where multiple edge servers each provide different
portions of the content to the client system, each edge server may
generate a download signature for a portion of the content, and the
download signatures may be combined to create a download signature
for the entire content. In an embodiment, the edge servers or the
client system may provide the download signature to a monitoring
system for comparison to the upload signature. Alternatively, the
edge servers may compare the download signature to the upload
signature. In another embodiment, a plurality of monitoring systems
can be distributed throughout the CDN, such as near the edge
servers. At 412, the download signature and the upload signature
can be compared to determine if the signatures match, as shown at
414. When the signatures match, the CDN can receive another request
for content at 406.
[0029] Alternatively, when the signatures do not match, an alert
can be generated, such as by creating a trouble ticket, to notify
CDN support staff of a problem with the delivery of the content. In
an embodiment, the alert may be sent to a centralized event
tracking system. The download signature may not match the upload
signature when a content object is stale, when there is a network
problem that prevents the delivery of a content object, or any
combination thereof. A content object may be stale when a new
version of the content object has been provided by the content
provider but has not propagated to the edge node providing the
content to the client system. Preferably, CDN support staff can
receive the alert substantially in real-time and can promptly
correct the issue causing the difference between the upload
signature and the download signature.
[0030] In an additional embodiment, the CDN can include one or more
autodownloader systems. The autodownloader systems can be located
throughout the CDN, such as close to the edge servers. The
autodownloader system can periodically download content from the
CDN, generate a download signature, and compare the download
signature to the upload signature for the content. The
autodownloader system can generate an alert, such as by creating a
trouble ticket for the CDN support staff, when the download
signature and the upload signature do not match. The autodownloader
system can provide a quality assurance measure of the delivery of
content even when users are not currently accessing the
content.
[0031] In an embodiment, the autodownloader system can generate a
screen capture image of the content. For video content, the
autodownloader system can generate multiple screen capture images,
preferably at a lower rate than the content, to verify that the
video content can be played back correctly. The screen capture
images can be provided to the CDN support staff to aid in resolving
delivery issues or to the content provider to allow for
verification of the quality of the CDN. Additionally, an audio
capture may be provided when the content includes audio data.
[0032] FIG. 5 shows an illustrative embodiment of a general
computer system 500. The computer system 500 can include a set of
instructions that can be executed to cause the computer system to
perform any one or more of the methods or computer based functions
disclosed herein. The computer system 500 may operate as a
standalone device or may be connected, such as by using a network,
to other computer systems or peripheral devices.
[0033] In a networked deployment, the computer system may operate
in the capacity of a server or as a client user computer in a
server-client user network environment, or as a peer computer
system in a peer-to-peer (or distributed) network environment. The
computer system 500 can also be implemented as or incorporated into
various devices, such as a personal computer (PC), a tablet PC, an
STB, a personal digital assistant (PDA), a mobile device, a palmtop
computer, a laptop computer, a desktop computer, a communications
device, a wireless telephone, a land-line telephone, a control
system, a camera, a scanner, a facsimile machine, a printer, a
pager, a personal trusted device, a web appliance, a network
router, switch or bridge, or any other machine capable of executing
a set of instructions (sequential or otherwise) that specify
actions to be taken by that machine. In a particular embodiment,
the computer system 500 can be implemented using electronic devices
that provide voice, video or data communication. Further, while a
single computer system 500 is illustrated, the term "system" shall
also be taken to include any collection of systems or sub-systems
that individually or jointly execute a set, or multiple sets, of
instructions to perform one or more computer functions.
[0034] The computer system 500 may include a processor 502, such as
a central processing unit (CPU), a graphics processing unit (GPU),
or both. Moreover, the computer system 500 can include a main
memory 504 and a static memory 506 that can communicate with each
other via a bus 508. As shown, the computer system 500 may further
include a video display unit 510 such as a liquid crystal display
(LCD), an organic light emitting diode (OLED), a flat panel
display, a solid-state display, or a cathode ray tube (CRT).
Additionally, the computer system 500 may include an input device
512 such as a keyboard, and a cursor control device 514 such as a
mouse. Alternatively, input device 512 and cursor control device
514 can be combined in a touchpad or touch sensitive screen. The
computer system 500 can also include a disk drive unit 516, a
signal generation device 518 such as a speaker or remote control,
and a network interface device 520 to communicate with a network
526. In a particular embodiment, the disk drive unit 516 may
include a computer-readable medium 522 in which one or more sets of
instructions 524, such as software, can be embedded. Further, the
instructions 524 may embody one or more of the methods or logic as
described herein. In a particular embodiment, the instructions 524
may reside completely, or at least partially, within the main
memory 504, the static memory 506, and/or within the processor 502
during execution by the computer system 500. The main memory 504
and the processor 502 also may include computer-readable media.
[0035] The illustrations of the embodiments described herein are
intended to provide a general understanding of the structure of the
various embodiments. The illustrations are not intended to serve as
a complete description of all of the elements and features of
apparatus and systems that utilize the structures or methods
described herein. Many other embodiments may be apparent to those
of skill in the art upon reviewing the disclosure. Other
embodiments may be utilized and derived from the disclosure, such
that structural and logical substitutions and changes may be made
without departing from the scope of the disclosure. Additionally,
the illustrations are merely representational and may not be drawn
to scale. Certain proportions within the illustrations may be
exaggerated, while other proportions may be minimized. Accordingly,
the disclosure and the FIGs. are to be regarded as illustrative
rather than restrictive.
[0036] The Abstract of the Disclosure is provided to comply with 37
C.F.R. .sctn.1.72(b) and is submitted with the understanding that
it will not be used to interpret or limit the scope or meaning of
the claims. In addition, in the foregoing Detailed Description of
the Drawings, various features may be grouped together or described
in a single embodiment for the purpose of streamlining the
disclosure. This disclosure is not to be interpreted as reflecting
an intention that the claimed embodiments require more features
than are expressly recited in each claim. Rather, as the following
claims reflect, inventive subject matter may be directed to less
than all of the features of any of the disclosed embodiments. Thus,
the following claims are incorporated into the Detailed Description
of the Drawings, with each claim standing on its own as defining
separately claimed subject matter.
[0037] The above disclosed subject matter is to be considered
illustrative, and not restrictive, and the appended claims are
intended to cover all such modifications, enhancements, and other
embodiments which fall within the true spirit and scope of the
present disclosed subject matter. Thus, to the maximum extent
allowed by law, the scope of the present disclosed subject matter
is to be determined by the broadest permissible interpretation of
the following claims and their equivalents, and shall not be
restricted or limited by the foregoing detailed description.
* * * * *
References